In a medium heat-proof bowl add chocolate, corn syrup, and salt.
Pour heavy cream into small saucepot and bring just to a boil. Pour over chocolate and allow to sit for about a minute.
Begin whisking in the center, gently and slowly, until an emulsion begins to form. The chocolate will look shiny and smooth. Then slowly begin to work your way out to the edges while whisking slowly, emulsifying all the chocolate and cream. When it is smooth and homogenous, whisk in the vanilla followed by the butter.
If the ganache looks broken, pour a small amount of cold whipping cream into the ganache and whisk gently. You can continue to add up to about ¼ cup, but you shouldn’t need to.
Tap the bowl on a folded towel to remove any large bubbles.
Pour into pre-baked tart shells. You can quickly hit the top with a kitchen torch to remove any surface bubbles if so desired.
Refrigerate until set. Top with flakey sea salt if desired.
Notes
Note: This make 1 large tart or 10, 2.5 inch mini tarts.